The present invention relates to a method of operating a hearing aid system. The present invention also relates to a hearing aid system adapted to operate according to said method.
Generally a hearing aid system according to the invention is understood as meaning any system which provides an output signal that can be perceived as an acoustic signal by a user or contributes to providing such an output signal and which has means which are used to compensate for an individual hearing loss of the user or contribute to compensating for the hearing loss of the user or contribute to compensating for the hearing loss. These systems may comprise hearing aids which can be worn on the body or on the head, in particular on or in the ear, and can be fully or partially implanted. However, devices like consumer electronic devices (televisions, hi-fi systems, mobile phones, MP3 players etc.), whose main aim is not to compensate for a hearing loss, may also be considered a hearing aid system, provided they have measures for compensating for an individual hearing loss.
Prior to use, the hearing aid is adjusted by a hearing aid fitter according to a prescription. The prescription is based on a hearing test, resulting in a so-called audiogram, of the performance of the hearing-impaired user's unaided hearing. The prescription is developed to reach a setting where the hearing aid will alleviate a hearing loss by amplifying sound at frequencies in those parts of the audible frequency range where the user suffers a hearing deficit.
In a traditional hearing aid fitting, the hearing aid user visits an office of a hearing aid fitter, and the user's hearing aids are adjusted using the fitting equipment that the hearing aid fitter has in his office. Typically the fitting equipment comprises a computer capable of executing the relevant hearing aid programming software and a programming device adapted to provide a link, between the computer and the hearing aid.
Within the present context a hearing aid can be understood as a small, battery-powered, microelectronic device designed to be worn behind or in the human ear by a hearing-impaired user. A hearing aid comprises one or more microphones, a battery, a microelectronic circuit comprising a signal processor, and an acoustic output transducer. The signal processor is preferably a digital signal processor. The hearing aid is enclosed in a casing suitable for fitting behind or in a human ear.
The mechanical design of hearing aids has developed into a number of general categories. As the name suggests, Behind-The-Ear (BTE) hearing aids are worn behind the ear. To be more precise, an electronics unit comprising a housing containing the major electronics parts thereof is worn behind the ear. An earpiece for emitting sound to the hearing aid user is worn in the ear, e.g. in the concha or the ear canal. In a traditional BTE hearing aid, a sound tube is used to convey sound from the output transducer, which in hearing aid terminology is normally referred to as the receiver, located in the housing of the electronics unit, and to the ear canal. In some modern types of hearing aids a conducting member comprising electrical conductors conveys an electric signal from the housing and to a receiver placed in the earpiece in the ear. Such hearing aids are commonly referred to as Receiver-In-The-Ear (RITE) hearing aids. In a specific type of RITE hearing aids the receiver is placed inside the ear canal. This category is sometimes referred to as Receiver-In-Canal (RIC) hearing aids.
In-The-Ear (ITE) hearing aids are designed for arrangement in the ear, normally in the funnel-shaped outer part of the ear canal. In a specific type of ITE hearing aids the hearing aid is placed substantially inside the ear canal. This category is sometimes referred to as Completely-In-Canal (CIC) hearing aids. This type of hearing aid requires an especially compact design in order to allow it to be arranged in the ear canal, while accommodating the components necessary for operation of the hearing aid.
Within the present context a hearing aid system may comprise a single hearing aid (a so called monaural hearing aid system) or comprise two hearing aids, one for each ear of the hearing aid user (a so called binaural hearing aid system). Furthermore the hearing aid system may comprise an external device, such as a smart phone having software applications adapted to interact with other devices of the hearing aid system. Thus within the present context the term “hearing aid system device” may denote a hearing aid or an external device.
The inventors have realized that it is an important issue for hearing aid systems that the performance of the microphones and receivers, may degrade due to normal aging, especially when the hearing aid system is worn in an environment with high humidity or when combined with significant exposure to water or sweat. The performance may also degrade due to rough handling, e.g. resulting from e.g. a hearing aid being dropped by the user. Furthermore, receiver distortion may vary greatly from one unit to the other due to the nature of the design. Reduced performance of the hearing aid system may have the consequence that the hearing aid system is not worn by a user or that a user having the hearing aid system on trial selects not to purchase it.
EP-B1-2177052 discloses a method of identifying a receiver in a hearing aid comprising the steps of measuring the impedance of the receiver using said hearing aid and identifying said receiver as one of several predetermined receiver models on basis of said impedance measurement.
EP-B1-2039216 discloses a method for monitoring a hearing device comprising an electro-acoustical output transducer worn at or in a user's ear or in a user's ear canal, wherein the electrical impedance of the output transducer is measured and analyzed, whereby the status of the output transducer and/or of an acoustical system cooperating with the output transducer, such as a tubing of a BTE hearing device, may be evaluated in a simple and efficient manner. Thereby it is enabled to automatically and immediately recognize when the output transducer or an acoustical system cooperating with the output transducer is blocked by ear wax or when the output transducer is damaged.
More specifically EP-B1-2039216 discloses that the measured electrical impedance as a function of frequency may be analyzed by comparing the measured electrical impedance to reference data stored in the hearing device, wherein such reference data may be generated in the manufacturing process of the hearing device.
According to one embodiment of EP-B1-2039216 the resonance frequency of the loudspeaker in free space is stored in a hearing device during the manufacturing process. Later, when the hearing device is operated, an analyzer unit generates the stored resonance frequency and measures the voltage on a resistor related to the loudspeaker at this frequency. If the measurement shows too much of a difference, an alarm signal is created.
US-B2-7302069 discloses a method wherein the acoustic conditions in the auditory canal, especially the acoustic impedance, are estimated by measuring the electrical input impedance of a hearing aid earpiece and wherein a mechanical resonance may be determined from the graph of the electrical input impedance and whereby a detected shift of the mechanical resonance can then be used for automatic correction of the normal frequency curve of the hearing aid.
However, none of the prior art is directed at detecting or compensating reduced hearing aid system performance due to non-linear effects in the receiver.
It is therefore a feature of the present invention to provide a method of operating a hearing aid system that can compensate for receiver distortion.
It is still another feature of the present invention to provide a hearing aid system adapted to compensate degraded receiver performance due to receiver distortion.